The placing of structural masonry and erection of steel were in progress between Fourth avenue and Irving place during the latter part of the year. On account of conditions arising from the state of war, steel deliveries could not be obtained for other parts of the work where short sections of excavation were completed. The work of excavating under the 14th Street station of the First Subway, in. Fourth avenue, was also necessarily deferred on account of the uncertainty in time of making steel deliveries.

The percentages of the principal items of work completed are as follows:

About 13 per cent of the total estimated value of the work is complete.

Route No. 8, Section No. 2.— The depth of the subgrade is 42 feet at the west end of the section, about 27 feet at Second avenue, and 32 feet at the east end of the section. The material in the excavation is sand, gravel, silt, hardpan and rock, the rock being encountered principally near the west end of the section, where it varies from 15 feet to 28 feet below the street surface. The cut and cover method is used in making the excavation.

During the early part of the year the contractor erccted working plants in 14th street between Third and Second avenues, between Second and First avenues, and between First avenue and Avenue A. Excavation was begun in May, and at the close of the year the top lift of excavation, about 10 feet in depth, had been taken out from Third to Second avenues, over a portion of the block between Second and First avenues and from First avenue to Avenue A. In the block between Third and Second avenues the work of carrying down sheeted pits for the insertion of long posts supporting the street decking system to subgrade preparatory to completing the excavation, was in progress. On account of delay in obtaining steel deliveries, the excavation was not advanced below the first lift, but as far as possible to do so,

the work has been carried on with the view of providing for the expeditious removal of the remaining excavation as soon as steel deliveries are made. During the latter part of the year shoring and underpinning the elevated railway structures at Second and Third avenues were in progress.

The percentages of the principal items of work completed are as follows:

Excavation

Steel delivered

Per cent

19

77

About 18 per cent of the total estimated value of the work is complete.

Route No. 8, Section No. 3.— The work on this section during the year consisted of the completion of the air-compressing plants and sinking of the shafts in Manhattan and Brooklyn, the building of eight tunnel shields, the driving of the headings out of the shafts, and the completion of the clay blanket for the permanent and temporary cover over the tubes near the Brooklyn pierhead line.

The air-compressing plants for this work are located at Avenue D and East 14th street, Manhattan, and at Kent avenue and North 7th street, Brooklyn. These plants are electrically operated by power obtained from the Edison companies. Each plant has a capacity of 28,000 cubic fect of free air per minute compressed to 45 pounds and 2,000 cubic feet of free air per minute compressed to 120 pounds. The installation of the high-pressure hydraulic pumps for furnishing power for shoving the shields and erecting the iron lining was also completed.

The shafts in Manhattan and Brooklyn were constructed of steel and concrete and sunk as caissons under compressed air. They were of such great depth that it was necessary to build and sink them in three sections.

The caisson for the Manhattan shaft, located at Avenue D and East 14th street, was placed under air pressure in January and reached subgrade in April. The bottom was then concreted and waterproofed and air taken off the shaft in May. This shaft was sunk to a depth of 90 feet below the street surface through filled ground, sand, clay and gravel. The maximum air pressure was 391/2 pounds.

The Brooklyn shaft, located near the bulkhead line at the foot of North 7th street, was placed under air pressure in February and reached subgrade in June. The bottom was then concreted and waterproofed and air taken off in July. This shaft was sunk through filled ground and timber cribbing for the first 27 feet, then through clay, and for the bottom 11 feet through rock, its bottom being 87 feet below the street surface. During sinking operations the air pressure averaged about 15 pounds, but while waterproofing and sealing the bottom was in progress, a maximum of 371/2 pounds was required.

In Manhattan two shields were assembled during May and June. The shields for the north river heading and the south land heading were started from the shaft under air pressure in July, and advanced for a distance of 65 feet when the heading face was sealed and the air removed from the tunnels in August and September, respectively. The shields for the south river and the north land headings were then constructed. The shaft was again placed under air pressure and these shields were started from the shaft in October and advanced 65 feet where the faces of the headings were sealed. Air pressure was again removed from the tunnels early in November.

The shaft cages were then installed, and the permanent tunnel bulkheads with air locks were constructed during November and the driving of the four headings under compressed air by the shield method was resumed. The maximum air pressure was 341/2 pounds.

In Brooklyn two shields were assembled during July and August. Early in October air was again placed in the shaft and the north river and south land shields were started. These shields were advanced 65 feet and the faces of the headings sealed. Air pressure was removed from the tunnels early in September. The other pair of shields for the north land and south river headings were then assembled, and early in October the shaft was again placed under air. These headings were advanced 65 feet from the shaft during October, and at the end of the month air was again removed from the tunnels.

Cages were then installed in the shaft and permanent tunnel bulkheads were constructed. The driving of the four tunnel shields